Reaction apparatus for carrying out exothermic and endothermic chemical processes with radial flow of a heat exchange medium

ABSTRACT

The reaction apparatus comprises an annular nest of contact tubes in a reaction tank and connected into headers at their opposite ends, for passage of the reaction gas through the contact tubes in contact with catalyst material in the tubes. A heat exchange medium is circulated by a fan, pump or the like through an external heat exchanger and is supplied and discharged through respective axially spaced annular supply and discharge conduits, to flow over the contact tubes. Baffles are arranged in the tank in a known manner to extend transversely of the length of the tubes to direct the heat exchange medium to flow alternately in opposed radial directions over the tubes between the supply and discharge conduits. At least one additional annular circuit is arranged at at least one point of the tank intermediate the supply and discharge conduits, is connected to the heat exchanger and the tank and supplies and discharges a regulable partial amount of the heat exchange medium. In one embodiment of the invention, several such additional annular conduits are arranged at respective points of the tank intermediate the supply and discharge conduits. In another embodiment of the invention, diaphragms or partitions divide the tank into separate compartments each of which has a respective heat exchanger associated therewith.

Unite States Patent [191 Wanlra et a1.

[ 1 Mar. 18, 1975 [73] Assignee: Deggendorfer Werft und Eisenbau GmbH, Deggendorf, Donau, Germany 22 Filed: Jan. 12, 1973 1211 Appl. No.: 323,224

[30] Foreign Application Priority Data Jan. 13, 1972 Germany 2201528 [52] US. Cl. 165/107, 23/288-M, 165/161 [51] Int. Cl. F28d 15/00, BOlj 9/00 [58] Field of Search 165/107, 159, 161; 23/288 K, 288 L, 288 M [56] References Cited UNITED STATES PATENTS 652,119 6/1900 Knietsch 23/288 K 688,472 12/1901 Knietsch 23/288 K 3,147,084 9/1964 Franzen 23/288 M 3,236,297 2/1966 Costesm. 165/107 3,353,923 11/1967 Peters..... 23/288 M 3,490,521 l/1970 Byerley 165/161 3,532,472 10/1970 Foster 23/288 M 3,566,961 3/1971 Lorenz 165/159 3,595,308 7/1971 Durdin... 3,623,549 11/1971 Smith 165/107 3,762,465 10/1973 Gutlhuber 165/107 FORElGN PATENTS OR APPLICATIONS 607,511 3/1926 France 165/107 917,306 l/l963 United Kingdom... 476,840 5/1929 Germany 165/107 Primary Examiner-Manuel A. Antonakas Assistant E.raminerDaniel J. OConnor Attorney, Agent, or FirmMcGl'ew and Tuttle [57] ABSTRACT Thereaction apparatus comprises an annular nest of contact tubes in a reaction tank and connected into headers at their opposite ends, for passage of the reac tion gas through the contact tubes in contact with catalyst material in the tubes. A heat exchange medium is circulated by afan, pump or the like through an external heat exchanger and is supplied and discharged through respective axially spaced annular supply and discharge conduits, to flow over the contact tubes. Baffles are arranged in the tank in a known manner to extend transversely olthe length of the tubes to direct the heat exchange medium to flow alternately in opposed radial directions over the tubes between the supply and discharge conduits. At least one additional annular circuit is arranged at at least one point of the tank intermediate the supply and discharge conduits, is connected to the heat exchanger and the tank and supplies and discharges a regulable partial amount of the heat exchange medium. In one embodiment of the invention, several such additional annular conduits are arranged at respective points of the tank intermediate the supply and discharge conduits. In another embodiment of the invention, diaphragms or partitions divide the tank into separate compartments each of which has a respective heat exchanger associated therewith.

11 Claims, 6 Drawing Figures SHEET 1 OF 4 PATENIEB MK I 81975 FIGJ PATEHTEB MAR l 8W5 SHEET 2v 0F 4 FIGB REACTION APPARATUS FOR CARRYING OUT EXOTHERMIC AND ENDOTHERMIC CHEMICAL PROCESSES WITH RADIAL FLOW OF A HEAT EXCHANGE MEDIUM FIELD AND BACKGROUND OF THE INVENTION This invention is directed to reaction apparatus for carrying out exothermic and endothermic chemical reactions and, more particularly, to an improved heat exchange arrangement for such reaction apparatus.

In a conventional design of such reaction apparatus, there is a tank in which there is arranged a vertical nest of contact tubes. These contact tubes, which contain a catalyst material, have their opposite ends secured, in a fluid-tight manner, into respective headers and open, at their opposite ends, into upper and lower hoods connected to the tank. The reaction gas flowing through the contact tubes is supplied and removed through these hoods.

In addition, a heat exchange medium generally is conducted through the space of the tank surrounding the contact tubes, in order either to absorb or to supplement the heat released or used up, depending on the type of the chemical process. The heat exchange medium is restored to its original temperature, after issuing from the tank, by a cooling device or a heating device, depending on the type of the chemical process, before the heat exchange medium is again directed into the tank for a further flow cycle.

In order to assure uniform external heat transfer contact between the contact tubes and the heat exchange medium, in the axially traversed central region of the heat exchanger, there are provided distributor plates or baffles defining flow cross sectional areas dimensioned and corresponding to the pressure loss of the heat exchange medium supplied and discharged, in the two end regions, transversely of the contact tubes and thus parallel to these distributor plates.

A predominantly transverse flow of the heat exchange medium with respect to the contact tubes, instead of the predominantly longitudinal flow, has already been provided by arranging deflecting plates or baffles which provide alternate flow cross sections on opposite sides thereof, as disclosed in German published Specification No. 1,039,040. However, such a flow course is not suitable for reaction apparatus with a high output, where the ratio of diameter to length of the reaction tank is relatively high, because of the large number of contact tubes. The flow resistance to the heat exchange medium through the many contact tubes extending in each course of the many deflections transverse to its direction of flow is likewise relatively high, because it requires, on the one hand, an uneconomically high circulation performance for the heat exchange medium and, on the other hand, an inadmissably large portion of the heat exchange medium flows through the gap between the various contact tubes and the deflecting plates or baffles.

The drawbacks of a purely transverse flow of the heat exchange medium can be avoided by a radial flow, where the heat exchange medium is conducted, inside the reaction taznk, by the arrangement of deflection plates or baffles having alternately a flow cross section in the center and a flow cross section on their outer edge, from the outside to the inside and from the inside to the outside. This arrangement is particularly suitable for ring-shaped or annular nests of tubes with a free central space and for heat exchangers, and is shown, for example, in British Pat. No. 310,157.

In connection with a radial flow, it is advisable to arrange ring or annular conduits at the two ends of the reaction tank, with openings distributed evenly over the entire circumference for the uniform supply and discharge of the heat exchange medium. This is also known as shown in German published application 1,601,162.

In this type of reaction apparatus, it is frequently tried to keep the temperature difference of the heat exchange medium as constant as possible, both in the horizontal section and between the inlet and outlet of the entire apparatus. In specific cases, it is necessary, however, not to keep the temperature constant along the contact tubes in order to achieve a maximum yield during thereaction.

SUMMARY OF THE INVENTION The present invention is based on the consideration of changing the temperature characteristic of the heat exchange medium along the contact tubes in a certain manner, and this requires additional measures to influence the elimination and the supply of heat. Accordingly, the invention comprises, in connection with the uniform supply and discharge of the heat exchange medium around the circumference, as well as the alternately radially inwardly and radially outwardly directed flow of the heat exchange medium, providing at least one additional ring circuit or annular conduit for the supply or discharge of an adjustable partial amount of the heat exchange medium, at at least one point intermediate the annular discharge and supply conduits at the respective opposite ends of the reaction chamber or tank.

In accordance with another feature of the invention, the gaps between the deflecting plates or baffles and the contact tubes are so designed that the transverse velocity of flow of the heat exchange medium is maintained substantially constant within a zone, which has the result that the heat transfer within a zone is also constant. In connection with varying intervals between the deflecting plates or baffles, it is also possible to achieve that the temperature differences and the pressure losses are reduced to a minimum in a horizontal section inside the zone.

In accordance with another feature of the invention, the reaction tank is divided, by separating partitions or diaphragms extending transversely of the contact tubes, into two or more sections, with separate inlets and outlets for the heat exchange medium being arranged for each section. In this connection, it is advisable to provide a separate circulating pump or fan and, if necessary, also a separate heat exchanger for each zone of the heat exchange medium conducted through a section of the reaction tank. It is even possible to use different heat exchange media separated from each other by partitions or diaphragms, or to use different contact materials for the respective regions of the contact tubes, or to do both.

An object of the invention is to provide an improved heat exchange arrangement for reaction apparatus for carrying out exothermic and endothermic chemical processes.

Another object of the invention is to provide such a heat exchange arrangement in which the temperature characteristic of the heat exchange medium longitudinally of the contact tubes of the reaction apparatus can be changed in a certain manner.

A further object of the invention is to provide such a heat exchange arrangement, for reaction apparatus in which the heat exchange medium is supplied and discharged through respective axially spaced annular supply and discharge conduits, in which at least one additional annular conduit, for the supply or discharge of an adjustable partial amount of the heat exchange medium, is provided at at least one point intermediate the supply and discharge conduits.

Another object of the invention is to provide such a heat exchange arrangement in which the transverse velocity of flow is kept substantially constant within the zone to maintain the heat transfer within the zone also constant.

A further object of the invention is to provide such a heat exchange arrangement in which the temperature differences and the pressure losses are reduced to a minimum in a horizontal section inside a zone.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings:

FIG. 1 is a vertical sectional view of a reaction tank, embodying the invention, with an external heat exchanger;

FIGS. 2 and 3 are diametric sectional views taken on the line ll-ll and Ill-Ill, respectively, of FIG. 1;

FIG. 4 is a vertical sectional view of another reaction tank embodying the invention and also provided with external heat exchanger means;

FIG. 5 is a vertical sectional view through still another reaction tank embodying the invention; and

FIG. 6 is a detailed sectional view illustrating the contact tubes as rolled to attain a fluid-tight fit in a partition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a substantially cylindrical reaction tank 1 has arranged therein a ring-shaped or annular nest of contact tubes 2 whose opposite ends are secured, in fluid tight relation, in upper and lower headers 3 and 4, respectively, and open into respective adjoining hoods or chambers 5 and 6. The contact tubes 2 are filled, as usual, with a catalyst material, and they are traversed by a reaction gas from either the top to the bottom or from the bottom to the top thereof.

Several horizontal deflecting plates or baffles extend transversely relative to contact tubes 2 in vertically spaced relation to each other, so as to leave flow cross sections therebetween. The deflecting plates or baffles are arranged in two groups, one comprising the deflecting plates or baffles 7 secured at their outer ends to the inner surface of the side wall of reaction tank 1 and the other comprising the deflecting plates or baffles 8 secured at their centers to a vertical tube 9. Deflecting plates 7 have their inner ends spaced from tube 9, and deflecting plates 8 have their outer ends spaced from the side wall or reaction tank 1. In addition, the deflecting plates or baffles have annular slots through which the contact tubes extend, and whose width, and thus the flow cross section, is slightly differently dimensioned, if necessary, in order to attain, by the resulting leakage currents, a possibly uniform velocity of flow and thus a possibly uniform heat transfer within the individual radial flow zones between the alternating deflecting plates and baffles 7 and 8.

For the supply and discharge of a heat exchange medium, which is to absorb the heat released in the contact tubes during the reaction when carrying out an exothermic chemical process, reaction tank 1 is connected at its upper and lower ends to respective ring or annular conduits 12 and 13 through respective openings 10 and 11 distributed substantially uniformly around the circumference of reaction tank 1. Annular conduits l2 and 13 are connected, by respective nipples 14 and 15, to the housing 16 of a cooler forming an external heat exchanger, and in which is arranged a spiral tube 17 having external inlets and outlets. In addition, an axial flow pump or fan, driven by an electric motor 18, is mounted from the top into the housing 16 of the heat exchanger.

At a point intermediate annular conduits l2 and 13 there are arranged, directly above and below an annular deflecting plate or baffle 7, having its outer periphery sealed to the shell or side wall of reactiontank 1, two additional annular conduits 20 and 21 which are also connected to the interior of reaction tank 1, surrounding contact tubes 2, through openings 22 and 23, respectively, distributed around the circumference. Annular conduits 20 and 21 are also connected, by nipples 24 and 25, respectively, to the cooler housing 16. The flow cross section of the nipples 24 and 25 can be varied by respective adjustable throttle elements 26 and 27.

The apparatus operatesin a manner which will now be described. The heat exchange medium, circulated by axial flow pump or fan 19 through reaction tank 1 and cooler housing 16 in the direction of the arrows, enters reaction,tank 1 through upper nipple 14, upper annular conduit 12 and the respective circumferentially spaced openings 10. From there, the heat exchange medium initially flows inwardly through the top section of contact tubes 2 between upper header 3 and the uppermost annular deflection plate or baffle 7. After reversal of the direction of flow in the tube-free central part of the interior of reaction tank 1, the heat exchange medium flows between the top deflection plate or baffle 7 and the deflection plate or baffle 8 immediately therebelow and radially outwardly toward the shell or side wall of reaction tank 1. These alternating inward and outward flows are repeated several times, until the heat exchange medium enters cooling housing 16 at the bottom end of reaction tank 1 through circumferential openings 11, annular conduit 13 and nipple 15 to give off the heat absorbed from the contact tubes 2 to the spiral tube 17 which is traversed by a cooling medium.

Since most of the heat is generated in the upper range of the reaction tank 1, a part of the heat exchange medium is returned to the cooler housing 16, after a corresponding temperature increase and inner deflection, by annular conduit 20 and nipple 24. Another part is returned to cooler housing 16 after the next inner deflection, through annular conduit 21 and nipple 25, while the balance of the heat exchange medium remains in reaction tank 1 to the bottom end thereof. By regulating the previously branched off partial amounts by means of the throttle elements 26, 27, it is possible to achieve a certain temperature characteristic of the heat exchange medium in the longitudinal direction of contact tubes 2 corresponding to the amount of heat, which varies from the top to the bottom.

FIGS. 2 and 3 illustrate, in a cross section through the annular conduits 12, 13 and the respective circumferential openings and 11, the uniform radial supply and discharge of the heat exchange medium.

FIG. 4 illustrates another arrangement of the circulating system for the heat exchange medium in accordance with the invention. In addition to the supply of the heat exchange medium through annular conduit 29 arranged at the upper end of reaction tank 28, and dis charged through an annular conduit 30 arranged at the bottom end, there is both an additional discharge and an additional supply of regulable partial amounts of the heat exchange medium at various levels between the upper and lower ends of the reaction tank 1. This is effected through a group of three annular conduits 31, 32 and 33 and a group of two annular conduits 34 and 35, whose nipples connecting the same to heat exchangers are provided with throttle elements 36. Annular conduits 31, 32 and 33, serving for the additional discharge of heat exchange medium, are connected to the suction side ofa circulating pump or fan 37 in a heat exchanger housing 39. Annular conduits 34 and 35, serving for the additional supply of heat exchange medium, are connected to the pressure side of a second circulating pump 38 in a respective heat exchanger housing 40.

In housing 39, there is arranged a spiral tube 41 traversed by a cooling medium and having external inlets and outlets, so that the partial amounts of the heat exchange medium discharged additionally through annular conduits 31, 32 and 33 are cooled to be returned conjointly through the top annular conduit 29 to reaction tank 28. The amounts of cooling medium and the amount of heat discharged are regulated by means of a valve 41a in dependence on the temperature at a certain point a in reaction tank 28.

In the range of the additional supply of regulable partial amounts of heat exchange medium, however, special cooling is not necessary as this is already effected by the mixing of the heat exchangemedium with the additionally discharged circulating partial amounts. The amount of heat thus withdrawn effects an intensive circulation in the lower range of reaction tank 28.

The desired temperature characteristic of the heat exchange medium, longitudinally of the contact tubes which have not been shown in FIG. 4, is obtained by adjusting throttle elements 36 in the cycle of the discharged and supplied partial amounts of heat exchange medium. These throttle elements can be adjusted initially by hand and can then remain in a certain adjusted position.

FIG. 5 illustrates an embodiment of the invention wherein a reaction tank 42 is divided, by separating partitions or diaphragms 43 and 44, into three superposed sections 42', 42" and 42" which are not connected with each other. As far as the operation is concerned, each of these three sections can be considered as a reactor or as any other heat exchanger with its own circulating pump and its own regulation. In section 42, the heat exchange medium is circulated by means of pump or fan 45, being supplied and discharged through annular conduits 46 and 47. Section 42 is exothermic, and has a lower temperature than the adjacent section 42". Regulation of section 42" is effected in a manner such that a partial amount of the relatively colder heat exchange medium, which can be varied by means of regulating element 48, is supplied from section 42". Adjustment of regulating element 48 is effected automatically in dependence on the temperature at a certain point b in section 42 of reaction tank 42.

An equal partial amount of the heat exchange medium is withdrawn from the cycle of section 42' through line 49 and is fed to the cycle of the adjacent section 42" in the range of the respective pump 50 and the spiral tube 51 traversed by a cooling medium. The temperature regulation of the heat exchange medium discharged in this region 42" through annular conduit 52 and supplied again through annular conduit 53 is effected by the amount of cooling medium flowing in spiral tube 51, and this latter amount can be regulated by means of regulating element 54.

Section 42" is endothermic and has a higher temperature level than the other two sections 42 and 42". In the case of section 42", the heat exchange medium, supplied through annular conduit 55 and discharged through annular conduit 56, and whose circulation is maintained by pump or fan 57, gives off heat to the contact tubes in the range adjacent section 42", and the heat thus given off is resupplied to the beating medium by the heating medium flowing through the spiral tube 58. The amount of heating medium is varied by means of a regulating element 59.

In section 42, the heat exchange medium is conducted radially to the nest of contact tubes only in the end regions adjacent annular conduits 55 and 56, as can be seen from the arrows, that is, transversely of the. individual contact tubes. In the interposed central region, the heat is conducted to the tubes parallel to the longitudinal extent of the latter. Such a flow course is attained, in a known manner, by the arrangement of the two deflecting plates or baffles 60 and 61 which delimit the central region with respect to the two end regions. Unlike the deflecting plates or baffles 7 and 8 of FIG. 1, which are arranged between two adjacent radial flow regions, baffles 60 and 61 extend across the entire interior of reaction tank 42 and have openings whose cross sections increase in correspondence with the pressure gradient on the inflow side of the plates or baffles in the range of the individual contact tubes, to achieve a uniform flow of the heating medium with respect to all the contact tubes, if at all possible.

For the supply and discharge of the heat exchange medium in the reaction tank 42, the annular conduits 46 and 47, 52 and 53, and 55 and 56 are arranged, in the embodiment of FIG. 5, inside the double-walled reaction tank. The deflection plates and baffles and the separating partitions or diaphragms extend up to the outer wall of the tank shell to delimit the annular conduits.

FIG. 6 is a detail view illustrating how a sealed relation or packing of the sections 42', 42" and 42' can be attained by rolling contact tubes 2 into the separating partitions or diaphragms 43 and 44.

It is also possible to arrange, in correspondence with the various reaction processes in individual sections inside the contact tubes, different catalysts, or inert materials, which can be separated from each other, if necessary, by corresponding superposed tube closers. Also, all embodiments of the invention with cooling devices can also be used in reaction apparatus for endothermic chemical processes. It is only necessary to replace the coolers by heaters to bring the heat exchange medium again to its original temperature, after it has given off its heat to the contact tubes.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a reaction apparatus for carrying out exothermic and endothermic chemical reactions, of the type having an annular nest of contact tubes in a reaction tank and over which a heat exchange medium, circulated by forced flow producing means through an external heat exchanger and supplied and discharged through respective axially spaced annular supply and discharge conduits connected to the heat exchanger, is directed to flow, the improvement comprising, in combination, baffle means arranged in said tank to extend transversely of the length of said tubes to direct the heat exchange medium to flow alternately in opposed radial directions over said tubes between said supply and discharge conduits; and at least one additional annular conduit, at at least one point of said tank intermediate said supply and discharge conduits, connected to said heat exchanger and said tank and supplying and discharging a regulable partial amount of the heat exchange medium.

2. In a reaction apparatus, the improvement claimed in claim 1, in which said tank has a cylindrical side wall and a support extending centrally axially thereof; said baffle means including first annular baffles secured at the radially outer ends to said circumferential wall and having radially inner ends spaced from said support, and second baffles secured to said support and having radially outer ends spaced from said cylindrical wall; there being two said additional annular conduits arranged on respective opposite sides of one of said first baffles and discharging a regulable partial amount of the heat exchange medium into said external heat exchanger.

3. In reaction apparatus, theimprovement claimed in claim 1, including respective conduits connecting each said additional annular conduit to the associated heat exchanger; and respective throttle valves in each conduit.

4. In reaction apparatus, the improvement claimed in claim 1, including a first series of said additional annular conduits communicating with an upper section of said reaction tank and withdrawing heat exchange medium from said reaction tank and discharging the withdrawn heat exchange medium into said heat exchanger for return to said annular supply conduit; and a second series of said additional annular conduits communicating with said reaction tank over a lower portion thereof and with said annular discharge conduit; said second series of additional annular conduits supplying heat exchange medium from said annular discharge conduit to said reaction tank.

5. In reaction apparatus, the improvement claimed in claim 1, including at least one partition extending transversely of said reaction tank and dividing said reaction tank into at least two sections; each section having respective inlets and outlets for the heat exchange medium.

6. In reaction apparatus, the improvement claimed in claim 5, in which said forced flow producing means comprises respective circulating pumps for each said reaction tank section operable to circulate the heat exchange medium through the respective reaction tank section. g

7. In reaction apparatus, the improvement claimed in claim 5, in which said contact tubes extend in fluidtight sealed relation through said partitions.

8. In reaction apparatus, the improvement claimed in claim 1, in which said baffle means comprises a series of baffles spaced apart axially of said reaction tank, each baffle being formed with openings through which said contact tubes extend; and each opening being larger than theadjacent contact tube to define an annular flow passage, and the passages in respective baffles having different sizes to attain a uniform heat transfer, between axially adjacent baffles, between the contact tubes and the heat exchange medium.

9. In reaction apparatus, the improvement claimed in claim 1, in which said baffle means comprises a series of baffles spaced apart axially of said tank; the axial spacing between adjacent baffles being adapted to the quantity of heat exchange medium flowing through each space defined by a pair of axially spaced baffles.

10. In reaction apparatus, the improvement claimed in claim 1, in which said reaction tank has a double side wall including inner and outer cylindrical walls spaced radially from each other; said annular conduits being defined, in part, by said inner and outer tank walls.

11. The improvement claimed in claim 5, in which the respective tube sections extending through each reaction tank section contain respective different filling materials. 

1. In a reaction apparatus for carrying out exothermic and endothermic chemical reactions, of the type having an annular nest of contact tubes in a reaction tank and over which a heat exchange medium, circulated by forced flow producing means through an external heat exchanger and supplied and discharged through respective axially spaced annular supply and discharge conduits connected to the heat exchanger, is directed to flow, the improvement comprising, in combination, baffle means arranged in said tank to extend transversely of the length of said tubes to direct the heat exchange medium to flow alternately in opposed radial directions over said tubes between said supply and discharge conduits; and at least one additional annular conduit, at at least one point of said tank intermediate said supply and discharge conduits, connected to said heat exchanger and said tank and supplying and discharging a regulable partial amount of the heat exchange medium.
 2. In a reaction apparatus, the improvement claimed in claim 1, in which said tank has a cylindrical side wall and a support extending centrally axially thereof; said baffle means including first annular baffles secured at the radially outer ends to said circumferential wall and having radially inner ends spaced from said support, and second baffles secured to said support and having radially outer ends spaced from said cylindrical wall; there being two said additional annular conduits arranged on respective opposite sides of one of said first baffles and discharging a regulable partial amount of the heat exchange medium into said external heat exchanger.
 3. In reaction apparatus, the improvement claimed in claim 1, including respective conduits connecting each said additional annular conduit to the associated heat exchanger; and respective throttle valves in each conduit.
 4. In reaction apparatus, the improvement claimed in claim 1, including a first series of said additional annular conduits communicating with an upper section of said reaction tank and withdrawing heat exchange medium from said reaction tank and discharging the withdrawn heat exchange medium into said heat exchanger for return to said annular supply conduit; and a second series of said additional annular conduits communicating with said reaction tank over a lower portion thereof and with said annular discharge conduit; said second series of additional annular conduits supplying heat exchange medium from said annular discharge conduit to said reaction tank.
 5. In reaction apparatus, the improvement claimed in claim 1, including at least one partition extending transversely of said reaction tank and dividing said reaction tank into at least two sections; each section having respective inlets and outlets for the heat exchange medium.
 6. In reaction apparatus, the improvement claimed in claim 5, in which said forced flow producing means comprises respective circulating pumps for each said reaction tank section operable to circulate the heat exchange medium through the respective reaction tank section.
 7. In reaction apparatus, the improvement claimed in claim 5, in which said contact tubes extend in fluid-tight sealed relation through said partitions.
 8. In reaction apparatus, the improvement claimed in claim 1, in which said baffle means comprises a series of baffles spaced apart axially of said reaction tank, each baffle being formed with openings through which said contact tubes extend; and each opening being larger than the adjacent contact tube to define an annular flow passage, and the passages in respective baffles having different sizes to attain a uniform heat transfer, between axially adjacent baffles, between the contact tubes and the heat exchange medium.
 9. In reaction apparatus, the improvement claimed in claim 1, in which said baffle means comprises a series of baffles spaced apart axially of said tank; the axial spacing between adjacent baffles being adapted to the quantity of heat exchange medium flowing through each space defined by a pair of axially spaced baffles.
 10. In reaction apparatus, the improvement claimed in claim 1, in which said reaction tank has a double side wall including inner and outer cylindrical walls spaced radially from each other; said annular conduits being defined, in part, by said inner and outer tank walls.
 11. The improvement claimed in claim 5, in which the respective tube sections extending through each reaction tank section contain respective different filling materials. 